Predictive value of cord blood hematological indices and hemoglobin Barts for the detection of heterozygous α-thalassemia-2 in an African- Caribbean population

Abstract

Background: Cord blood hemoglobin Barts (HbBarts) and hemocytometric indices may be used for classification of newborns into those without α- thalassemia-2 (αα/αα) and with heterozygous α-thalassemia-2 (- α3.7/αα). We investigated by logistic regression analysis whether the combination of HbBarts and hemocytometric indices improves classification compared with classification based on a single analyte. Methods: HbBarts percentages and hemocytometric indices were determined in cord blood of 208 consecutive newborns in Curacao (Netherlands Antilles). Of these, 157 had αα/αα and 51 had -α3.7/αα, as established by DNA analysis. Results: Between-group differences were significant for erythrocytes, mean cell volume, mean cell hemoglobin (MCH), mean cell hemoglobin concentration, platelets, hemoglobin F0 (HbF0), and HbBarts. The Logit equation of the logistic regression model, using MCH (pg) and HbBarts (%), was: 42.7164 + 5.7916(HbBarts) 1.3110(MCH). A sensitivity of 100% was reached at a Logit value of -3.70. The corresponding specificity was 62.2%, and the predictive value of a positive test (PV+) was 46.3% (95% confidence interval, 37.0- 55.7%). The relative information gains were as follows: 88% for the HbBarts- MCH combination, 26% for MCH (not significant), and 0% for HbBarts compared with the 24.6% -α3.7/αα prevalence. Conclusion: Combined use of cord blood HbBarts and MCH improves classification compared with classification based on single hemocytometric indices.